1. Field of the Invention
The present invention relates to a semiconductor laser used in an optical disk system, optical communication, and the like, and particularly to a ridge-structure-type, discrete and monolithic semiconductor laser.
2. Description of the Background Art
In a semiconductor laser with a double-channel ridge structure, a ridge is formed between channels (trenches) having a small equivalent refractive index, and the channels are formed between layers having a large equivalent refractive index.
In such a conventional double-channel ridge structure semiconductor laser, the trenches on the sides of the ridge have a width of 10 μm, and the trenches are formed by removing semiconductor film by dry-etching and wet-etching.
The laser light emitted from the semiconductor laser thus constructed exhibits an oval far-field pattern, where the expansion of the far-field pattern is large in the direction normal to the active layer and the expansion of the far-field pattern is small in the direction horizontal to the active layer.
Conventional double-channel ridge structure semiconductor lasers have a problem that their yields are unsteady because the intensity center and shape of the far-field pattern in the horizontal direction tend to fluctuate with variation of the optical output.